Relative Permeability Functions for Tertiary Polymer Flooding

The surprising high efficiency of waterflood and polymer flood in heavy oil reservoirs has attracted interest in the recent years. The ability to model these unstable immiscible processes needs further development. The conventional approach is to start from waterflood matched relative permeabilities and add bulk polymer viscosity and retention in porous medium. This procedure will modify the fraction flow curves and thereby make changes to the fluid flow. However, comparing to experimental results this straight forward procedure gives poor prediction and leads to underestimation of oil production and overestimation of the differential pressure. We have compared derived relative permeabilities from the mention approach to history matched oil production, water breakthrough, and differential pressures from experiments and also more complex approaches including in-situ oil saturation distribution after waterflooding. Earlier published experimental results including in-situ saturations have been used for interpretation of flow description. Oil mobilization by polymer injection leads to cross flow of oil into established water channels (from experimental observations), and we use the dynamic in-situ saturation development in water channels and bypassed zones for history match. The paper describes oil mobilization and differential pressure for polymer flooding especially at adverse mobility ratio and also the changes in relative permeability from match on production and pressure to also anchor relative permeability on in-situ oil saturation distribution (including dynamic cross flow between waterflooded and bypassed zones). The relative permeabilities generated by different simulation approaches showed large variations. The paper discusses guidelines for polymer flood relative permeabilities.